[dpdk-dev] [RFC v2] net: fix rte_vlan_insert with shared mbuf

[Stephen Hemminger <stephen@networkplumber.org>]

If mbuf is shared then rte_vlan_insert() would clobber the original
Ethernet header. The changed version handles this by getting
an mbuf that will hold the new Ethernet and VLAN header followed
by another mbuf (cloned) for the data.

Fixes: c974021a5949 ("ether: add soft vlan encap/decap")
Signed-off-by: Stephen Hemminger <sthemmin@microsoft.com>
---
v2 - compile tested only, do copy/clone.

 lib/librte_net/rte_ether.h | 37 ++++++++++++++++++++++++++++---------
 1 file changed, 28 insertions(+), 9 deletions(-)

diff --git a/lib/librte_net/rte_ether.h b/lib/librte_net/rte_ether.h
index c2c5e249ffe9..5fc306e5d08c 100644
--- a/lib/librte_net/rte_ether.h
+++ b/lib/librte_net/rte_ether.h
@@ -374,10 +374,10 @@ static inline int rte_vlan_strip(struct rte_mbuf *m)
  * Software version of VLAN unstripping
  *
  * @param m
- *   The packet mbuf.
+ *   Pointer to the packet mbuf.
  * @return
  *   - 0: On success
- *   -EPERM: mbuf is is shared overwriting would be unsafe
+ *   -ENOMEM: could not allocate mbuf for header
  *   -ENOSPC: not enough headroom in mbuf
  */
 static inline int rte_vlan_insert(struct rte_mbuf **m)
@@ -385,15 +385,34 @@ static inline int rte_vlan_insert(struct rte_mbuf **m)
 	struct ether_hdr *oh, *nh;
 	struct vlan_hdr *vh;
 
-	/* Can't insert header if mbuf is shared */
-	if (rte_mbuf_refcnt_read(*m) > 1) {
-		struct rte_mbuf *copy;
+	/* Can't safely directly insert header if mbuf is shared or indirect */
+	if (!RTE_MBUF_DIRECT(*m) || rte_mbuf_refcnt_read(*m) > 1) {
+		struct rte_mempool *mp = (*m)->pool;
+		struct rte_mbuf *md, *mh;
+
+		mh = rte_pktmbuf_alloc(mp);
+		if (unlikely(mh == NULL))
+			return -ENOMEM;
+
+		mh->tx_offload = (*m)->tx_offload;
+		mh->vlan_tci = (*m)->vlan_tci;
+		mh->vlan_tci_outer = (*m)->vlan_tci_outer;
+		mh->port = (*m)->port;
+		mh->ol_flags = (*m)->ol_flags;
+		mh->packet_type = (*m)->packet_type;
 
-		copy = rte_pktmbuf_clone(*m, (*m)->pool);
-		if (unlikely(copy == NULL))
+		md = rte_pktmbuf_clone(*m, mp);
+		if (unlikely(md == NULL)) {
+			rte_pktmbuf_free(mh);
 			return -ENOMEM;
-		rte_pktmbuf_free(*m);
-		*m = copy;
+		}
+
+		mh->next = md;
+		mh->nb_segs = md->nb_segs + 1;
+		memcpy(rte_pktmbuf_append(mh, ETHER_HDR_LEN),
+		       rte_pktmbuf_mtod(md, void *), ETHER_HDR_LEN);
+		rte_pktmbuf_adj(md, ETHER_HDR_LEN);
+		*m = mh;
 	}
 
 	oh = rte_pktmbuf_mtod(*m, struct ether_hdr *);
-- 
2.17.1